For each role on a chef server, display the number of servers with that role.

role_counter.sh

#!/bin/bash
set -e

if ! which knife; then
    ( >&2 echo "Couldn't find knife on your path!" )
    exit 1
fi

# Redirecting stderr to /dev/null will make output clean.
ROLES=$(knife role list 2>/dev/null)

# Bash delimits on whitespace, so you can use this to iterate over every role on the chef server.
for ROLE in $ROLES; do
    # the -e flag returns the number of matches.
    SERVER_COUNT=$(knife search "role:$ROLE" 2>/dev/null | grep -e "Node Name" )
    echo "$SERVER_COUNT $ROLE"
done